Hello from the New York City heat dome. According to the weather experts, this is a dome of high pressure that traps an unhealthy mix of heat and humidity. I chose not to mention this fact when I dragged the iPhone 16 Pro Max and Samsung Galaxy S25 Ultra out of the lush office air conditioning and into the 98-degree atmosphere of nearby Bryant Park. I had an extreme test in mind, and the less my AI-powered handsets knew about it, the better.
After slathering my bald dome with sunblock and grabbing a lukewarm bottle of water, I walked into the park and found a spare chair and table. I hoped to position myself in the shade with these two excellent flagship phones in direct sunlight.
I wanted to know how long it would take for either one of them to overheat.
With the temps at 98 degrees and the real-feel around 105 degrees Fahrenheit, this might seem cruel, but there's real purpose here. In the Northern Hemisphere, we're fully immersed in a steamy summer, but it'll get around to the rest of you below the equator in due time. No matter where you live, we all take our phones everywhere, including to the beach, amusement parks, and other places where there's sun, fun, and lots of heat.
Your smartphone is designed to handle some of it. Its CPU, after all, generates heat. The iPhone 16 line uses graphene sheets to disappate heat, while the Samsung Galaxy S25 Ultra has a vapor chamber. These are helpful, and nine times out of ten, they'll keep the phones cool and in working order.
What these heat dissipation systems are not designed to manage is the act of being baked, and that, my friends, is what I did to these phones.
First, I stripped both devices of any protective coverings, like a case. After that, I made sure the screens would stay on (always with the iPhone, 10 minutes with the Galaxy). I gingerly place them, screens up, on the table, set a stopwatch, and backed away.
Even though I tried to keep myself in the shade, I was mostly in the sun as I chronicled the total lack of activity on each phone. Time goes slowly when you're melting under a heat dome.
With sweat trickling down my back, I looked at both screens at around the two-minute mark. Even with their sunlight-beating nits, I could barely make out what was on each screen (I was also wearing sunglasses, which did not help).
At roughly four minutes in, the iPhone 16 Pro Max switched to a "Temperature" screen, featuring a red thermometer and the message that the "iPhone needs to cool down before you can use it."
You might be thinking, "Oh, the iPhone lost!" I disagree. Instead of letting the iPhone get hotter through operation, it basically went into protection mode and, with that message, alerted me to get it the hell out of the sun. I complied and put the incredibly hot phone in my pocket.
The Samsung Galaxy S25 Ultra was still functional, in that the touchscreen responded to my touch. However, a few minutes later, I noticed an overheating message at the top of the screen: "Device Overheating. Tap here for details." That's a strange way to let someone know the phone is getting too hot. I prefer the iPhone's more alarmist method.
A minute or so after that, I found that the phone was shutting down apps because of overheating. Finally, I noticed that while the screen responded, I couldn't open a single app, again, because of "overheating."
So while the Samsung Galaxy S25 Ultra looked like it was still working, it was, just like the iPhone 16 Pro Max, rendered useless by the extreme heat.
And so was I.
I grabbed the S25 ultra off the table – it felt almost hot enough to cook an egg – and carefully dropped it into my pocket where it all but seared my thigh.
One long swig of water later and I was headed back indoors.
Within five minutes, both phones had recovered and were fully functional.
In the end, I'd say the Samsung Galaxy S25 Ultra is slightly better at handling the heat (it might be that vapor chamber) but not so much that it'll matter to you. The real lesson here is that, as hardy as iPhone 16 Pro Max and Samsung Galaxy S25 Ultra appear, even they are no match for a heat dome.
Keep cool and keep those phones out of the sun.
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